Metastasis is one of the leading causes of cancer-related deaths worldwide. This is caused by circulating tumor cells (CTCs), originating from a primary tumor, extravasating at a distant location and forming secondary tumors. In my first two years as a graduate student I successfully worked to characterize a novel process of extravasation stem cells use to exit blood vessels, termed angiopellosis (Allen et al. Stem Cells 2016). This was followed by the discovery that cancer/tumor cells also possess the ability to extravasate through both angiopellosis. Interestingly, cancer/tumor cells can utilize angiopellosis to extravasate while maintaining a multicellular/cluster phenotype. The goal of this F31 proposal is to better understand how circulating tumor cells (CTCs) utilize angiopellosis to extravasate as multicellular clusters, and how this affects their metastatic potential. To understand the dynamics of cancer/tumor cell angiopellosis, I will use a transgenic zebrafish embryo model Tg(fli1a:egfp) in which the vascular dynamics can be visualized, in vivo. The model also allows for easy manipulation of blood vessels on the cellular and molecular level. I will examine the effect of candidate molecules, VEGF and Plakoglobin, on CTC cluster extravasation. These molecules have been previously correlated with cancer metastasis and CTC clusters. Additionally, we will isolate tumor cells undergoing angiopellosis elucidate the gene profile, and validate these finding in a mouse xenograft model. I hypothesize that angiopellosis extravasation allows for the CTC clusters to have increased and metastatic potential. This project will be the first to study CTC clusters using angiopellosis as a means for extravasation and shed more light on why their metastatic potential is higher than single CTCs.